And to single nyets, are you in the "move-in together as soon as you can afford to" camp, or "delay it even when you already can coz reasons" camp?
Living habits play a huge role in cohabitating happily in the long term personally. Having fun and enjoying each other's company won't have much mileage if you can't stand each other's living habits!
For some, you may live together way longer than you'd be in love with each other even >.>
Sharing a home together also gives you an idea on how responsible, proactive, clean and how well they manage and balance chores, duties, and time together. In my (limited) experience, most people who has never lived on their own, generally do not take the initiative or have the know how to fix, improve and maintain a house. I suppose that's not important for some.. but for me who's always taken care of her own space and prioritises on efficiency, I have my way of doing things and living together first can help us optimise ourselves to each other, or it can also highlight just how incompatible we might be. If anything, I'd say this is just as important to a relationship as any, if not the most.
So, for you non-single nyets: any inputs? How soon did you guys move in?
It's a no brainer for cohabitation to happen before even hatching the idea to get married. Aside from surfacing red flags, it can also help convince that the partner is the right one. The couple must experience and resolve a major conflict in a cohabitation environment, otherwise they will forever be beholden to sunk cost fallacy (where one side unwillingly concedes "because already married and don't want to break"). You must understand what you're getting into, and cohabitation is the only way.